1. Field of the Disclosed and Claimed Inventive Concepts
The presently disclosed process(es), procedure(s), method(s), product(s), result(s), and/or concept(s) (collectively referred to hereinafter as the “present disclosure”) relates generally to an aqueous coating composition comprising at least 0.5 wt % of a lactam-functionalized polymer comprising a polymer backbone and at least one lactam moiety attached to the polymer backbone. The aqueous coating composition can increase an open time of a water-borne latex paint. In particular, the polymer backbone can be polyacetal polyether, polyhemiaminal polyether, or polyaminal polyether. Additionally, the present disclosure also relates generally to a method of increasing an open time for an aqueous coating composition of a water-borne latex paint using the lactam-functionalized polymer.
2. Background and Applicable Aspects of the Presently Disclosed and Claimed Inventive Concept(s)
Open time is a property of a paint that is of high importance to the painter. It is defined as the maximum time the paint can be re-worked prior to demonstrating permanently the deformations brought to the paint, such as brush-marks, etc. Water-borne latex paints are known to suffer from a rather short open time in comparison to solvent borne paints. The origin of this difference lies in the fact that the binder in water borne paints is not soluble in the continuous phase (water).
One of the traditional methods to increase open time of paint is to add co-solvents and coalescing agents. Alkylene glycols are typically used as open time additives to improve the open time of paints by slowing down the rate of evaporation and preventing coalescence of latex particles that can be measured by diffusion wave spectroscopy (DWS). Although alkylene glycols can extend open time, they also contribute to volatile organic compound (VOC). Another disadvantage of the addition of solvents is the lowering of block resistance, and dirt pick-up can become a problem. Removing the solvent, particularly in high volume solids formations with low water content creates challenges for paints. The demand for low to zero VOC in paints requires other solutions for extending open time than the addition of co-solvents but maintaining paint rheology such as viscosities.
Nonionic synthetic associative thickeners (NSAT) has been developed and used to improve the rheology of a paint at various shear levels. These thickeners include hydrophobically-modified water-soluble polymers. They undergo intermolecular association in aqueous solution and thereby exhibit enhanced solution viscosity. They can also adsorb onto the dispersed-phase particles of an aqueous dispersion and thereby form a three-dimensional network. Typically, about 0.25 wt % to about 0.50 wt % of the active NSAT are used to significantly improve the paint rheology.
It has been found that coating compositions containing at least 0.5 wt % of a lactam-functionalized polymer comprising a polymer backbone and at least one lactam moiety attached to the polymer backbone can increase an open time of an aqueous coating composition while keep the desired rheology properties of the coating composition.